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  • Provide Solution For R.D. Sharma Maths Class 12 Chapter 30 Probaility Exercise 30.5 Question 18 Maths Textbook Solution.

Provide Solution For  R.D. Sharma Maths Class 12 Chapter 30 Probaility  Exercise 30.5 Question 18 Maths Textbook Solution.

Answers (1)

Answer:\frac{67}{256}

Hint: You must know the rules of finding probability functions.

Given: Bag contains = (4W+5R+7B) balls

Solution

No. of white balls = 4

No. of black balls = 7

No. of red balls = 5

 

Total balls = 16

 

No. of ways in which 4 balls can be drawn from 16 balls=16C_{4}

Let A = getting at least two white balls = getting 2, 3, 4 white balls

No. of ways of choosing 2 white balls =4C_{2}\times 12C_{2}

No. of ways of choosing 3 white balls =4C_{3}\times 12C_{1}

No. of ways of choosing 4 white balls =4C_{4}\times 12C_{0}

\begin{aligned} &P(A)=\frac{4 C_{2} \times 12 C_{2}+4 C_{3} \times 12 C_{1}+4 C_{4} \times 12 C_{0}}{16 C_{4}} \\ &=\frac{4 !}{2 ! 2 !} \times \frac{12 !}{2 ! 10 !}+\frac{4 !}{3 !} \times \frac{12 !}{11 !}+\frac{4 !}{4 ! 0 !} \times \frac{12 !}{12 !} \\ &=\frac{16 !}{4 ! 2 !} \\ &=\frac{67}{256} \end{aligned}

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